1. Field of the Invention
The present invention relates to an apparatus and a process for regulating gas injection for artificial lift of fluids in oil and gas wells.
2. Prior Art
Gas lift valves are utilized in connection with artificial lift procedures in downhole oil and gas wells. Pressurized gas, such as natural gas, is injected from the surface into the annulus formed by downhole production tubing and an outer casing. The well fluid inside the production tubing exerts hydrostatic pressure that increases with well depth. The injection of gas reduces the weight of the hydrostatic column, thus reducing the back pressure on the formation by reducing density and allowing reservoir pressure to push a mixture of produced fluids and gas up to the surface. In addition, as the gas rises, the gas bubbles help force or push the produced fluids, such as oil, ahead of or with them. The pressurized gas may be injected at a single point downhole below the fluid level or may be supplemented by multi-point injection.
The so-called lift gas is injected downhole into the production tubing to the produced fluid stream through one or more valves that are set at specified depths. The lift gas and the formation fluids are thereby forced and produced to the surface. At the surface, the injected gas and the liquids are thereafter separated. The gas may then be treated and either sent to compression or sent for sales.
It is desirable to stabilize the tubing pressure downhole within a certain range based on the gas supply pressure and based on the production rate.
The present invention automatically provides an apparatus and a process to regulate the gas injection rate so that the tubing pressure is stabilized within a certain range based on the gas supply pressure and based on the production rate.